Fabrication of Ir-CoO@mesoporous SiO Nanoreactors for Selective Hydrogenation of Substituted Nitroaromatics.

Nanosized Ir catalysts suffer from serious side reactions and poor stability during hydrogenation of substituted nitroaromatics to produce aromatic amines. In this work, core-shell nanostructures with sub-4 nm Ir-CoO hybrid cores and mesoporous SiO shells were designed and prepared to overcome these problems. The Ir-CoO hybrid cores were converted from IrCo alloy nanoparticles (NPs) inside SiO through in situ calcination and reduction pretreatments. The SiO mesoporous shells in Ir-CoO@SiO nanoreactors prevented the agglomeration/sintering of IrCo NPs, while allowing the free reactants and products (big molecules). The synergy between Ir and CoO species improved H adsorption, thus affecting the reaction rate as well as the selectivity to aromatic amines. As a result, the obtained Ir-CoO@SiO nanocatalyst showed tremendous improvement in catalytic activity, selectivity, and stability.